118P - High dose chemo-radio-immunotherapy for NSCLC III: ESR/ATS thresholds for DLCO correlate with radiation dosimetry and predict pneumonitis

Background

Durvalumab following chemoradiotherapy for non-small cell lung cancer (NSCLC) UICC stage III has become the standard of care in the past few years. With this treatment approach 5-year overall survival has risen to 50% for PD/PDL-1-positive patients. Therefore pulmonary function (PF) after treatment is of high importance in long term survivors. In this respect carbon monoxide diffusing capacity (DL_CO), which represents the alveolar compartment, was found to be a suitable measure for residual pulmonary capacity. The aim of the current analysis was to correlate pre-treatment DL_CO with the occurrence of pneumonitis and to model DL_CO decline after therapy to the total radiation dose within a defined lung volume.

Methods

Eighty-five patients with histologically confirmed NSCLC III treated between 2015/10 and 2020/10 were eligible for this study. Patients received two cycles of platinum-based induction chemotherapy followed by high dose radiotherapy and Durvalumab maintenance for one year. The clinical endpoints were based on the thresholds published by the European Respiratory Society. Pre-treatment DL_CO of 60% was correlated to the incidence of pneumonitis and DL_CO decline of 10% within three months after treatment was related to radiation dose.

Results

Patients with a pre-treatment DL_CO below 60% had a higher probability for pneumonitis grade 2 or higher (N = 71, one-sided Pearson correlation coefficient −0.183, p-value 0.063), which became significant in the subgroup of patients without Durvalumab (N = 40, one-sided Pearson correlation coefficient −0.306, p-value 0.027). The decline in DL_CO > 10% after the end of radiotherapy depended on the size of the lung volume receiving 45% to 65% (V_65%−45%) of the total radiation dose (one-sided Pearson correlation coefficient = 0.264, p-value = 0.019).

Conclusions

The current analysis revealed that DL_CO is a predictor for clinically relevant pneumonitis and a monitoring tool for post-treatment lung function as it correlates with radiation dose. This underlines the importance of peri-treatment lung function testing.

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.